1. Field of the Invention
The present invention relates to a display device and a display panel driver, and more particularly to a display device in which multiple display panel drivers are cascade-connected.
2. Description of the Related Art
When a large-sized display panel (for example, a liquid crystal display panel and an electroluminescence display panel) is driven, multiple data drivers are generally used to drive the data lines (or the signal lines). In such configuration, the data drivers are often cascaded-connected. The cascade connection of the data drivers eliminates the necessity of using a TCP (tape carrier package) technique, and this is advantageous to reduce the cost. In this case, a supply of the image data to each data driver is performed by supplying the image data to the data driver located on the end and by transferring the image data to the adjacent data driver by each data driver.
FIG. 26 is a block diagram showing an example of the configuration of the display device in which data drivers are cascaded-connected. Shown in FIG. 26 is the configuration of a liquid crystal display device as an example. The liquid crystal display device as shown in FIG. 26 is, for example, disclosed in Japanese Patent Application Publication No. P2001-174843A. The liquid crystal display device 101 of FIG. 26 is configured to receive image data 103 and synchronization data 104 from an image drawing unit 102 (for example, a CPU), and to display an image in response to these data. In detail, the liquid crystal display device 101 includes a liquid crystal display panel 105, a timing controller 106, a gate driver 107, and data drivers 108. The gate driver 107 drives gate lines provided in the display area 105a of the liquid crystal display panel 105, and the data drivers 108 drive data lines provided in the display area 105a. The timing controller 106 supplies gate side control signals 109 to the gate driver 107, and also supplies data control signals 111 to the data drivers 108, thereby controlling the gate driver 107 and the data drivers 108.
In addition, the timing controller 106 supplies the image data 110 to each data driver 108. The image data 110 are transferred in the following manner to a desired data driver 108. The timing controller 106 transmits the image data 110 to the leftmost data driver 108 regardless of the actual destination of the image data 110 to be transferred. The leftmost data driver 108 transfers the transmitted image data 110 to the data driver 108 adjacent on the right. Similarly, upon receipt of the image data 110 from the data driver 108 adjacent on the left, each data driver 108 transfers the transmitted image data 110 to the data driver 108 adjacent on the right. Each data driver 108 fetches the transmitted image data 110 when the received image data 110 are data addressed to itself, and drives the data lines of the liquid crystal display panel 105 in response to the fetched image data 110.
The transfer of the image data 110 between the data drivers 108 is most typically performed through interconnections formed on a glass substrate of the liquid crystal display panel 105. Although it is possible to transfer the image data 110 between the data drivers 108 by lead wires, interconnections formed on a glass substrate are generally used for the data transfer in view of easy implementation.
In a display device in which data drivers are cascade-connected, there are generally two problems as follows: A first problem is that an increasing number of interconnections are required to be arranged on a glass substrate due to the increase of the number of display grayscale levels of the liquid crystal display device. The increase of the number of interconnections makes the actual implementation on the glass substrate difficult; this is one of the serious problems in view of the easiness of the implementation. Another problem is that there is a necessity for fast data transfer due to the enhancement of the definition of the liquid crystal display panel (that is, the increase of the number of pixels).
With respect to these problems, Japanese Patent Application Publication No. P2001-174843A discloses an approach adopting a fast serial interface; however, use of a fast serial interface on a glass substrate is technologically difficult, since interconnections on the glass substrate have high impedances.
On the other hand, Japanese Patent Application Publication No. P2006-350341A discloses a technique for reducing the necessary data transfer speed by distributedly transferring the image data from both of the right and left sides of the display panel by the timing controller. However, according to the technology disclosed in this literature, the data drivers directly receiving the image data from the timing controller and the other data drivers are different in configuration; data drivers of two different configurations are required in a single display apparatus. Further, the data drivers directly receiving the image data from the timing controller are mounted with a line memory to distribute the image data to the adjacent data drives. Hence, the technology disclosed in Japanese Patent Application Publication No. P2006-350341A suffers from a problem of increase in the cost.
As thus discussed, according to the study of the inventor, these conventional technologies are not effective approaches to the problems of the increase in the number of interconnections and the necessity of fast data transfer.